Command-Tab is a known shortcut that allows switching between applications. Press and hold Command, then press and release Tab (while holding Command), and OS X will show a strip of large app icons across the screen, letting you easily switch applications by pressing Tab (forward), tilde/backquote (backward), the mouse, or many other methods.

But say you are switching between one of your Safari windows and a specific Pages document, or whatever, and you don't need to see the app switcher every time. You can switch back and forth between them without seeing the app switcher. To do so, press and release Command and then Tab quickly, making sure you press Command first.

When done right, you won't even see the app switcher icons; you'll simply flip between the last two programs you've used. This is useful when you have lots of windows open, and every time you select one application, its windows cover other apps' windows.

[robg adds: This works in 10.5 and 10.6, and perhaps even 10.4. I thought we had covered it in a prior hint, but I couldn't find it when searching. If you find it's a duplicate, please let me know.]

It definitely works in 10.4 (Tiger). Triggering it seems to depend on how quickly you release command after pressing tab - you can hold command for a while before pressing tab and/or hold tab for a while after releasing command. However, continuing to hold command for any appreciable period of time after pressing tab will show the icons.

I believe it has been stated before.
It not only works in 10.4 it works in 10.3 (maybe 10.2).
If you can't make it work without seeing the App Switcher, keep practicing. This is what makes copy and paste between to programs so easy. Try this, place your thumb over the command key and your index finger over the tab, then as you press the command key, twist your wrist, you finger will go down and your thumb will come up.

The hint as written doesn't work for me. If I press and release Command, then press and release Tab, nothing happens. You need to to press Command, then press Tab, then release Command, then release Tab. And do it all very quickly.

I honestly couldn't believe this was being published now. If this truly hasn't been posted before, than I don't understand how it slipped for so many years. This is roughly equivalent to "did you know you can change the icon for a hard drive?" at this point.

Yes, this has been available since 10.2 and possibly earlier (a prior comment couldn't verify before 10.4).

Sorry if I sound negative, but I'm really that surprised. This is something every Mac user I know is aware of. It's something that is easily stumbled upon without being told.

I agree this is excessively obvious. Arguably it's a duplicate of robg's own hint from 2002, although back then it worked with the Dock instead of a bezel. Users who haven't already seen this in action are the same people who find it difficult to hit the key combo that fast even when they try.